The U.S. has seen a steady decline in cancer mortality rates since 1993, but the overall decrease is relatively slight, due in part to insufficint treatment strategies for invasive and metastatic disease. This stems in part from our incomplete understanding of the genetic changes that promote metastatic behavior in cancer cells. Lack of such knowledge hinders the development of new therapies to target altered cellular pathways leading to metastasis. Our long-term goal is to define genetic pathways that drive tumor induction and metastasis in order to reveal novel therapeutic targets. The objective here is to build a mutagenesis system that will identify genes that cooperate in tumor progression to metastasis. We previously developed a robust transposon somatic mutagenesis strategy in zebrafish that leads to tumor induction in adult tissues and identification of cancer genes. We propose to expand our original system so it is applicable to both somatic and germ line mutagenesis. Inducible and germ line targeted transposase sources will be created for use with existing Gal4 driver lines. We have designed a novel gene breaking transposon containing a fluorescent reporter to capture expression of coding and noncoding genes. The fluorescence reporter will allow single cells to be followed during tumorigenesis after transplantation into wil type recipients. We will test the ability of our mutagenesis system to promote metastatic behavior in combination with a retinal tumor model we recently isolated in our laboratory. Transposon integration site analysis will be carried out on single cells exhibiting metastatic behavior. The goal is to identify gene pathways that correlate with metastatic behavior of individual cancer cells. Our rationale for the pro- posed work is that our mutagenesis system in combination with zebrafish models of adult and childhood cancers will identify new genes that cooperate in tumor onset and metastasis. This information can be expected to reveal new therapeutic targets for treating metastatic diseases.